SUP GUYS! I have added a bunch of upgrades as I'm sure we all have and now I'm faced with problems with air/fuel adjustments, MAP issues and idle characteristic problems. How far can we push the limits of the OEM PCM, sensors and adjustments before we need to look at an engine management system. Am I already there? I have a fully ported and polished TPI set-up from base to throttle body and a new roller cam kit from Comp cams that I'm afraid to get into cause the car already won't run right just with the small mods I've already done. This is my first speed density car but my 5th third gen. I'm very familiar with the car but can't seem to overcome this one! frustrated Should I be looking at fuel mgmnt systems already? or am I missing some good old fashioned technique?

 

What do your datalogs show?

What issues are you seeing/experiencing?

Post the mods.

 

Well, I have added 1''5/8 headers, lower temp fan switch with matching thermo, 42lb injectors,upgraded fuel pump, filter, holley AFPR, and deleted the A.I.R system as well as the smog pump, MSD 6AL ignition. I have no datalogs cause the car still has the OEM PCM. The only code I've ever got is 33 which is a MAP sensor and I replaced it. The problem is: With the MAP disconnected it will idle and run fine but(very rich) and eventually load up and stall out (too much fuel) with the MAP plugged in it searches for an idle runs lean and stalls. I have opened up the AFPR all the way to try to get 47-50 psi before I plug in the MAP but can only get 40-43 and when I plug the MAP in the pressure drops to low to sustain idle.

 

1) PCM = Power-train Control Module
2) ECM = Engine Control Module
3) The PCM did not arrive on the F-body until 1994.

The problem is the ECM program has limits and when you start doing modifications you are starting push those limits... You have reached the point when you should consider making your own BINS to compensate for your modifications.

 

OK! So I have already looked into Halteck systems(plug and play eng mgmnt sys) and a few others but I'm looking at $1000.00 and up. Is there a cheaper alternative? Sorry about the ECM/PCM I run them together sometimes, I also have a 96' SS which took very well to all the upgrades I put on it with no issues or changes to the PCM

 

Build a LS1 harness for your SBC

Theres a sticky about it in the TPI forum

 

The 96 should take easier to upgrades because they run a MAP & MAF IIRC... not a 4th genner tho so I could be wrong.

The 90-92 used a SD style or MAP only (manifold Air Pressure) whereas the 85-89 used a MAF only system. The MAF (Mass Air Flow) system takes very well to modifications, the MAP only system does not. Where you are looking at $1000 for an aftermarket system, you can buy all the stuff you need to burn your own ships for around $100 IIRC (It has been a while since I purchased my equipment). It takes a little time getting up and going, but once you do you can do a ton with it and it rewarding...

John

John

 

i think you have other issues with your car. i have a map car and it handled all the mods you have plus a small cam without any real trouble. it wasn't as fast as it should have been because it wasn't tuned for it. but it still was my daily at that point and ran fine.

the 42lb hr injector's are a bit much thou, the biggest i ran was 30s but i do have 42s now with boost and have run it off the stock chip just to check some stuff and it still pulled a lot of extra fuel out of it and ran. it didn't die like your car.

i think you need to buy a cable and get some data out of your car and fix whats wrong with the map sensor. than go from there into diy tuning. it can be done for less than 300$ these days if you already have a laptop. but it will mean a lot of time spend reading how to do everything. its not always easy for everyone. the learning curve is kinds steep.

 

And my experience has shown that the difference between a MAF car needing a new custom chip and a MAP car needing a new custom chip is a very small gap. MAP cars are not as sensitive to mods as the myths have you believe, and MAF cars are not as "self-compensating" either.

90-ROC, I think the 42lbs injectors are killing you more than anything else. Plus as ??? said you might have other physical issues with the car that we cant diagnose for you.